1. Field of the Invention
The present invention pertains to antimicrobial compositions that are stable in the presence of transition metals, nonaqueous compositions containing a transition metal and the antimicrobial composition, and a method for protecting a substrate from microbial infestation with the antimicrobial composition. The antimicrobial composition comprises a halopropynyl compound and an organic epoxide.
2. Description of the Background
Both exterior and interior surfaces, substrates of all types and organic compositions and formulations, when exposed to common environmental conditions, are prone to attack, discoloration and various kinds of destruction by a variety of species of microorganisms, including fungi, algae, bacteria and protozoa. As a result, there has always been a great need for effective and economical means to protect commercial compositions and formulations from the deterioration and destruction caused by such microorganisms, and to do so for an extended period of time.
There are a variety of materials which need protection against such microorganisms including, for example, materials such as paints and other coating formulations, surfactants, proteins, starch-based compositions, inks, emulsions and resins, stucco, concrete, stone, and cementaceous surfaces, wood, caulking, sealants, leather, plastics, and textiles. Other important commercial materials such as polymer dispersions or aqueous latex paints containing polyvinyl alcohol, polyacrylates or vinylpolymers, thickener solutions containing cellulose derivatives, kaolin suspensions and metal working fluids, also are prone to degradation by the action of objectionable microorganisms, which can significantly impair the usefulness of such compositions. Such degradation may produce, inter alia, changes in pH values, gas formation, discoloration, the formation of objectionable odors, and/or changes in rheological properties.
Wooden objects, in particular, are subject to degradation from a wide variety of natural pests. Fungi are particularly prevalent and include brown rots, white rots and soft rots. Fortunately, a variety of compositions have been developed for treating wooden objects and other materials and surfaces to retard the destructive effect of such pests.
A great deal of effort has gone into developing a wide variety of materials which, to various degrees, are effective in retarding or preventing the growth of, and accompanying destruction caused by, such microbes in a variety of circumstances. Such antimicrobial compounds include halogenated compounds, organometallic compounds, quaternary ammonium compounds, phenolics, metallic salts, heterocyclic amines, formaldehyde donors, organosulfur compounds and the like.
One of the most effective and best known classes of biocides used in such compositions are those containing a halopropynyl moiety, and especially an iodopropynyl moiety. Such compounds are widely disclosed in the patent literature including U.S. Pat. Nos. 3,660,499; 3,923,870; 4,259,350; 4,592,773; 4,616,004 and 4,639,460 to name a few. Included within this class of compounds are the halopropynyl carbamates which are known primarily for their fungicidal activity. Among these is 3-iodo-2-propynyl butyl carbamate, also referred to as IPBC, which is one of the best known and probably the most widely used of the halopropynyl carbamate fungicides. It is a highly active broad spectrum fungicide and, in addition to its fungicidal activity, it has also been associated with algaecidal activity as disclosed in Great Britain Patent 2,138,292 and U.S. Pat. Nos. 4,915,909 and 5,082,722.
Despite their wide acceptance, the halopropynyl carbamate biocides have been reported to be prone to degradation under certain conditions. In many of these instances, the degradation is minor, and while it may sometimes result in some discoloration and yellowing, a sufficient degree of antimicrobial protection usually remains.
A different and more significant form of degradation appears to occur in the presence of transition metals. Certain transition metals appear to cause significant destruction of halopropynyl compounds which can result in the loss of their ability to prevent microbial growth. This can be particularly troublesome in alkyd based coating systems where transition metals are used routinely in a number of pigments and, more importantly, in drier systems. The use of transition metals in such solvent based systems can cause a slow, but definite, degradation of the halopropynyl compounds. For this reason, the use of halopropynyl compounds as antimicirobial agents in nonaqueous compositions containing transition metals, especially alkyd coating compositions, has been disfavored.
The present invention addresses the destruction of halopropynyl compounds in the presence of certain transition metals and provides means for inhibiting said destruction.